Thermoelectric module and manufacturing method for same

ABSTRACT

A thermoelectric module and method of manufacture thereof, capable of preventing short-circuits between electrodes due to solder without causing increases in size or cost. A thermoelectric module is configured with lower electrodes formed on the inside surface of a lower substrate, placed in opposition to an upper substrate, on the inside surface of which are formed upper electrodes; the end faces of thermoelectric elements are soldered to the lower electrodes and upper electrodes. Each of the electrodes is configured from three layers, which are a copper layer, a nickel layer formed on one face of the copper layer, and a gold layer formed on one face of the nickel layer; a visor portion, protruding outward, is formed in the nickel layer, so that when positioning the thermoelectric elements above the electrodes and soldering the electrodes to the thermoelectric elements, the flowing of solder  18   a  from the side portions of electrodes to the insulating substrate is prevented.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a thermoelectric module which performsthermoelectric conversion, and to a manufacturing method for same.

Priority is claimed on Japanese Patent Application No. 2005-37767, filedFeb. 15, 2005, the content of which is incorporated herein by reference.

2. Description of Related Art

Thermoelectric modules, which utilize the Peltier effect and the Seebeckeffect in thermoelectric power conversion, have conventionally been usedin heating and cooling equipment and other applications. Suchthermoelectric modules are configured by forming multiple electrodes atprescribed locations on the opposing inside surfaces of a pair ofinsulating substrates, and by soldering the upper and lower ends ofthermoelectric elements to the opposing electrodes, to fix in placemultiple thermoelectric elements between the pair of insulatingsubstrates.

Among such thermoelectric modules, there are devices having a structurewhich prevents the occurrence of short-circuits across electrodes due tothe flow of solder in the molten state on the insulating substrates whensoldering the thermoelectric elements to the electrodes. Among thesedevices, there are thermoelectric modules in which electrodes areconfigured from three layers, which are a copper layer, a nickel layerformed over the entire surface of the copper layer, and a metal platedlayer of gold or similar formed on the upper surface (the upper surfacewhen forming the electrodes) of the nickel layer, and in which thenickel layer which has less solderability is exposed on the sidesurfaces of the electrodes (see for example, Japanese Unexamined PatentApplication, First Publication No. 2004-140250).

There are also devices in which grooves are provided between theelectrodes on the insulating substrates, to prevent the flow of solderin the molten state onto other electrodes (see for example, JapaneseUnexamined Patent Application, First Publication No. 2003-100983).

However, of the above-described thermoelectric modules, the formerentails the difficulty of processing to cause the nickel layer to beexposed on the side faces of the electrodes, as a result of which thereare the problems that the number of processes is increased, productionyields are lowered and manufacturing times lengthened, and in additioncosts are increased. In methods to manufacture such thermoelectricmodules, prior to removal by-etching of the unwanted portions of themetal plated layer (the side-face portions of the electrodes), resist isformed on the upper surface of the metal plated layer; and there is theproblem that during this processing, a shift in the electrodes and maskcauses resist to touch the side faces of electrodes, giving rise toshort-circuits.

Further, in the case of the latter thermoelectric modules of the priorart, grooves are formed between the electrodes on the insulatingsubstrates respectively, so that the distances between electrodes areincreased, and there is the problem that the thermoelectric modules areincreased in size (with reduced densities). Moreover, because groovesare formed, the number of processes is increased, production yields arelowered and manufacturing time is prolonged as well as increased costs.

The present invention was devised in order to address theabove-described problems, and has as an object the provision of athermoelectric module and manufacturing method for a thermoelectricmodule capable of preventing short-circuits between electrodes due tosolder, without resulting in increases in size or cost.

SUMMARY OF THE INVENTION

In order to attain this object, a thermoelectric module of thisinvention is configured by forming electrodes at prescribed locations onthe opposing inside surfaces of a pair of insulating substrates,arranged in opposition, and by soldering the end faces of a plurality ofthermoelectric elements to the respective opposing electrodes, to fixthe thermoelectric elements between the pair of insulating substrates,and is characterized in that a visor portion, protruding outward, isformed on the edge portion of the thermoelectric element-side portion ofthe electrodes, and when thermoelectric elements are positioned on theupper sides of electrodes and electrodes soldered to thermoelectricelements, the solder is prevented from flowing from the side portions ofthe electrodes to the insulating substrates.

In a thermoelectric module of this invention configured in this way, anoutward-protruding visor portion is formed on the upper-end edgeportions (the portions on the upper side when performing soldertreatment) of electrodes to be fixed to thermoelectric elements withsolder; hence when using solder to fix the lower-end portions ofthermoelectric elements to the upper faces of electrodes positioned onthe upper surface of an insulating substrate, molten-state solder whichhas overflowed from bonded portions accumulates on the upper faces andside faces of the visor portions.

As a result, events in which the solder flows as far as the insulatingsubstrate surface, making contact with solder which has flowed fromother electrodes and causing short-circuits between electrodes, can beprevented. Further, when fixing the other end portions of thermoelectricelements to electrodes formed on the other insulating substrate also,with the insulating substrate positioned below, by fixing the lower endportions of the thermoelectric elements to the upper faces of electrodespositioned on the upper surface of the insulating substrate, flowing ofsolder to the insulating substrate can be prevented.

Other configuration characteristics of a thermoelectric module of thisinvention are the formation of electrodes from a plurality of layersconsisting of metal layers of different types, and the formation in thevisor portion of a metal layer with less solderability with respect tothe solder, among the metal layers making up the plurality of layers.

Here, the less solderability with respect to solder generally indicatesa property of strongly repelling solder. In this invention, “lesssolderability” is taken to mean that, in tests in conformance with JIS C0053 (1996), the time interval A-t0 (known in the industry as thezero-cross time) stipulated is 3 seconds or longer. This test isperformed by plotting, against time, the change in force when aspecimen-is immersed in molten solder; the zero-cross time is the timefrom the start of immersion of the specimen in the solder vat, until thestate in which the force with which the specimen is pushed upward fromthe solder vat is in equilibrium with the force pulling the specimeninto the solder vat (force due to solderability).

By forming a visor portion in this metal layer with less solderability,flowing of solder in the molten state past the visor portion from theside faces of electrodes to the side of the insulating substrate can beprevented more reliably. Further, in this case the layer in which thevisor portion is formed is not limited to the uppermost layer among theplurality of layers, but can be any metal layer in a position in which avisor portion can be formed in a state maintaining a prescribed intervalfrom the insulating substrate. Metals having less solderability withrespect to solder include nickel and magnesium. Conversely, metalshaving good solderability with respect to solder include gold, tin, tinalloys (tin-antimony, tin-bismuth, tin-copper, tin-copper-silver) andsimilar.

Still another configuration characteristics of a thermoelectric moduleof this invention is the configuration of electrodes from three layers,which are a copper layer formed on one face of the insulating substrate,a nickel layer formed on one face of the copper layer, and a gold layerformed on one face of the nickel layer, and with the visor portionformed in the nickel layer.

Because of its superior conductivity, copper is widely used inelectrodes, and because of its superior solderability with respect tosolder, gold is appropriate as the surface layer of electrodes when anelectrode is to be fixed to a thermoelectric element by means of solder.And by forming a layer of nickel, with less solderability with respectto solder, between the copper layer and the gold layer, causing the edgeportion of the nickel layer to protrude so as to form a visor portion,flowing of molten-state solder to the side of the insulating substratecan be reliably-prevented. In this case, the peripheral portion of thegold layer may be formed to protrude toward the outside together withthe nickel layer visor portion; however, the side portion of the visorportion must be exposed without being covered.

Still another configuration characteristics of a thermoelectric moduleof this invention is the configuration of electrodes from a single layerconsisting of a metal layer of one type. In this case the metal used inthe metal layer is required to have superior conductivity and also tohave less solderability with respect to solder, and so it is appropriatethat nickel or magnesium be used. By this means, although the strengthof adhesion of electrodes and thermoelectric elements due to the solderis somewhat weaker, the reliability with which short-circuits betweenelectrodes due to solder can be prevented is increased. Further, becausethe number of processes for forming electrodes is reduced,thermoelectric modules can be easily manufactured, and costs can bereduced. Still another configuration characteristics of a thermoelectricmodule of this invention is the setting of both the thickness of thebase end and protrusion length of the visor portion to 1 μm or greater.Here, the base end of the visor portion is the border portion betweenthe main portion of the electrode and the visor portion. By this means,when soldering electrodes and thermoelectric elements, the visor portioncan be ensured to be sufficiently strong and long enough to prevent theflow of molten solder.

A method of manufacture of thermoelectric modules of this invention, inwhich electrodes are formed in prescribed locations on the opposinginside surfaces of a pair of insulating substrates, arranged inopposition, and the end faces of a plurality of thermoelectric elementsare soldered to the respective opposing electrodes, to fix in place thethermoelectric elements between the pair of insulating substrates, ischaracterized in having a resist layer formation process of forming aresist layer on one surface of the insulating substrates; an exposureprocess of exposing the surface of the resist layer, in a state ofmasking prescribed portions of the surface of the resist layer formed inthe resist layer formation process; a development process of removingthe masked portions in the resist layer through development of theresist layer exposed in the exposure process; an electrode formationprocess of forming electrodes, consisting of a plurality of metallayers, between the resist layer of prescribed shape formed in thedevelopment process; a resist layer removal process of removing theresist layer of prescribed shape; and, an visor formation process ofremoving a portion of the side portion of a metal layer on theinsulating substrate side, among the plurality of metal layers of theelectrodes, to form a visor portion on the edge portion of theelectrodes.

By this means, a simple method can be used to obtain a thermoelectricmodule in which the flowing of solder to the insulating substrates isprevented, and short-circuits between electrodes due to solder do notoccur. The resist layer formed in the resist layer formation process isnot limited to direct formation on one surface of the insulatingsubstrates, but may be formed via a prescribed seed layer. When forminga seed layer, this seed layer is removed by ion beam etching afterremoval of the resist layer.

In this case, the visor portion can be formed in the metal layer withless solderability with respect to solder among the plurality of metallayers making up the electrodes formed in the electrode formationprocess. Further, the electrodes formed in the electrode formationprocess can consist of three metal layers, which are a copper layerformed on one surface of the insulating substrates, a nickel layerformed on one surface of the copper layer, and a gold layer formed onone surface of the nickel layer, and the visor portion can be formed inthe nickel layer.

Another method of manufacture of thermoelectric modules of thisinvention, in which electrodes are formed in prescribed locations on theopposing inside surfaces of a pair of insulating substrates, arranged inopposition, and the end faces of a plurality of thermoelectric elementsare soldered to the respective opposing electrodes, to fix in place thethermoelectric elements between the pair of insulating substrates, ischaracterized in having a resist layer formation process of forming aresist layer on the upper surfaces of the insulating substrates; anexposure process of exposing the surface of the resist layers, in astate of masking prescribed portions of the surface of the resist layersformed in the resist layer formation process; a development process ofremoving the masked portions in the resist layers through development ofthe resist layers exposed in the exposure process; an electrodeformation process of forming electrodes, in which the top-end edgeportion is formed into a visor portion, between the resist layer formedinto a prescribed shape in the development process and in a portion ofthe surface of the resist layer; and, a resist layer removal process ofremoving the resist layer of prescribed shape.

By this means, a simple method can be used to obtain a thermoelectricmodule in which the flowing of solder to the insulating substrates isprevented, and short-circuits between electrodes due to solder do notoccur. In this case, electrodes formed in the electrode formationprocess may be configured from single layers consisting of a single typeof metal layer, or may be configured from a multilayer film consistingof a plurality of metal layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an oblique perspective figure showing the thermoelectricmodule of one embodiment of the invention;

FIG. 2 is a front view of the thermoelectric module shown in FIG. 1;

FIG. 3 is a cross section showing the state of an insulating substratefixed to a thermoelectric element via an electrode;

FIG. 4 is a cross section showing an electrode formed on-an insulatingsubstrate;

FIG. 5A-D shows processes for formation of electrodes, in which FIG. 5Ais a cross section of resist, FIG. 5B is a cross section showing thestate in which a copper layer, nickel layer, and gold layer are formedwithin the resist; FIG. 5C is a front view showing the state in whichresist has been removed; and, FIG. 5D is a front view showing the stateof formation of an electrode;

FIG. 6 is a cross section showing the state of an electrode fixed to athermoelectric element by solder;

FIG. 7 is a cross section showing thermoelectric elements fixed to theupper faces of electrodes formed on an insulating substrate;

FIG. 8 is a cross section showing an electrode with a thermoelectricelement in another embodiment;

FIG. 9A-C shows processes for formation of the electrode shown in FIG.8, where FIG. 9A is a cross-sectional view of resist, FIG. 9B is across-sectional view showing the state of formation of electrodesconsisting of a copper layer in resist, and FIG. 9C is a front viewshowing the state of formation of an electrode with the resist moved;and,

FIG. 10 is a cross-sectional view showing an electrode with athermoelectric module in still another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention are explainedreferring to the drawings. FIG. 1 and FIG. 2 show a thermoelectricmodule 10 of one embodiment. This thermoelectric module 10 has a pair ofinsulating substrates, which are a lower substrate 11 a and an uppersubstrate 11 b; lower electrodes 12 a are formed in prescribed positionsof the upper surface of the lower substrate 11 a, and upper electrodes12 b are formed in prescribed positions of the lower surface of theupper substrate 11 b. The lower-end faces of multiple thermoelectricelements 13, consisting of chips, are fixed in place to the lowerelectrodes 12 a by solder; and, the upper-end faces are fixed withsolder to the upper electrodes 12 b respectively, to integrally link thelower substrate 11 a and the upper substrate 11 b.

The lower electrodes 12 a and upper electrodes 12 b are installed atpositions shifted distances equal to substantially the width of one ofthe thermoelectric elements 13. Upper electrodes 12 b are bonded to theupper-end faces of two thermoelectric elements respectively while thereare two types of lower electrodes 12 a, one is bonded to the lower-endface of only one thermoelectric element 13, and another is bonded to thelower-end faces of two thermoelectric elements 13. Lower electrodes 12 ato which the lower-end face of only one thermoelectric element 13 isbonded are provided in two corner portions on one side (the rear-endportion in FIG. 2) of the lower substrate 11 a; lead wires 14 a, 14 bare connected to the rear-side portions of these lower electrodes 12 a,enabling connection to external equipment.

The lower substrate 11 a and upper substrate 11 b consist of sheets ofalumina; the thermoelectric elements 13 consist of alloy derived frombismuth-tellurium and are formed in a rectangular parallelepiped shape.Each of the thermoelectric elements 13 is electrically connected to thesubstrates via the lower electrodes 12 a and upper electrodes 12 b. Thelower-end faces of the thermoelectric elements 13 and lower electrodes12 a, the upper-end faces of the thermoelectric elements 13 and theupper electrodes 12 b, and the rear-side portions of the lowerelectrodes 12 a formed in edge side of the lower substrate 11 a and thelead wires 14 a, 14 b, are respectively fixed in place using solder.

The lower electrodes 12 a and upper electrodes 12 b are formed intosubstantially the same shape, configured as shown in FIG. 3. In thefollowing explanations, the lower electrodes 12 a and upper electrodes12 b are both described as electrodes 12, and the lower substrate 11 aand upper substrate 11 b are both described as insulating substrates 11.The electrodes 12 are configured as three metal layers, which are acopper layer 15 formed on the upper surface of the insulating substrate11, a nickel layer 16 formed on the upper surface of the copper layer15, and a gold layer 17 formed on the upper surface of the nickel layer16.

On the periphery of the nickel layer is formed a visor portion 16 a,protruding outward from the outer-circumference face of the copper layer15, so that a step is formed between the nickel layer 16 and the copperlayer 15. The gold layer 17 is formed on the upper surface of the nickellayer 16, in a state which causes the portion in proximity to the sideface at the side-face portion and upper face of the nickel layer 16 tobe exposed slightly. By using solder 18 to bond the upper face of theelectrode 12 to the lower-end portion of the thermoelectric element 13,the electrode 12 and thermoelectric element 13 are fixed in place.

When the electrode 12 is an upper electrode 12 b, the vertical-directionpositional relationship of the insulating substrate 11, electrode 12,and thermoelectric element 13 are inverted from the vertical-directionstate in FIG. 3. The thickness of the copper layer is set to 50 μm, thethickness of the nickel layer 16 is set to 4 μm, and the thickness ofthe gold layer 17 is set to 0.3 to 0.4 μm. The protrusion length a ofthe visor portion 16 a shown in FIG. 4 is set to from 1 to 5 μm. As thesolder 18, a solder of tin and antimony is used.

Next, a method of manufacture of a thermoelectric module 10 configuredas described above is explained. The thermoelectric module 10 ismanufactured by a manufacturing method having the processes shown inFIG. 5 and FIG. 6. In this case, a seed layer (not shown) consisting ofa chromium layer and a copper layer is first formed on the upper surfaceof the insulating substrate 11 by sputtering (a method in which a highdirect-current voltage is applied to an insulating substrate 11 and atarget (of the material used to deposit the layer, in this case,chromium and copper) while introducing argon gas into an vacuum, so thationized argon gas collides with the target and causes target material tobe ejected and deposited on the insulating substrate 11).

Dry film is applied to the upper surface of the seed layer, and using anexposure system (not shown) with prescribed areas masked, the surface isexposed for 120 seconds at an intensity of 150 mJ/cm2, after whichdevelopment is performed for 2.5 minutes in a sodium carbonate solutionat a temperature of 30 C. By this means, a pattern is formed in theresist 19 on the upper surface of the insulating substrate 11, as shownin (a) of FIG. 5. This resist 19 is formed in portions in which,ultimately, electrodes 12 will not be formed on the upper surface of theinsulating substrate 11.

A copper plating solution of 80 g/L of sulfuric acid, 190 g/L of coppersulfate, and 50 ppm of chlorine ions are used to perform plating at roomtemperature at a current density of 2 A/dm², to form a copper layer 15 awithin the resist 19 (see FIG. 5B). The thickness of this copper layer15 a is set to approximately 40 to 100 μm. Then, a nickel platingsolution of 240 g/L nickel sulfate, 45 g/L nickel chloride, and 6 g/Lboric acid is used to perform plating at a temperature of 55 degreesCelsius at a current density of 2 A/dm² , to form a nickel layer 16 ofthickness 4 μm on the upper surface of the copper layer 15 a within theresist 19.

Then, the nickel layer 16 is immersed in a plating bath set to atemperature of 55 degrees Celsius, and by passing a current at currentdensity 0.4 A/dm², a gold layer of thickness approximately 0.3 to 0.4 μmis formed on the upper surface of the nickel layer 16. By this means, asindicated in FIG. 5B, three metal layers, which are a copper layer 15,nickel layer 16, and gold layer 17 are formed within the resist 19.Next, a sodium hydroxide solution is used to remove the resist 19, andion beam etching (a method in which a specimen is treated by means ofthe sputtering reaction of an ion beam pulled from an ion source andaccelerated) is used to remove the seed layer formed below the resist19, resulting in the state in FIG. 5C.

Then, a prescribed thickness is removed by immersing the side-faceportion of the copper layer 15 a in etching solution for 30 seconds,resulting in the state FIG. 5D. By this means, an electrode 12consisting of the copper layer 15, the nickel layer 16 with a visorportion 16 a, and the gold layer 17 is formed on the prescribed portionof the surface of the insulating substrate 11. Though not shown in thedrawing, a seed layer consisting of a chromium layer and a copper layeris formed between the insulating substrate 11 and the copper layer 15;this seed layer is also contained in the electrode 12. The electrodes 12shown in FIG. 4 and in FIG. 5D are, for convenience of explanation,shown with different shapes; but in substance they are the same.

Next, on the upper face of the electrode 12 formed on the upper surfaceof the insulating substrate 11 through the processes shown in FIG. 5, athermoelectric element 13 is positioned, and soldering is performed.Here, first a solder layer, of tin and antimony, is formed on the uppersurface of the electrode 12. Then, the end portion of two or of onethermoelectric element is placed on the upper faces of each of theelectrodes 12, and a weight or other member is used to maintain thisstate. In this state, the insulating substrate 11 is then inserted intoa reflow furnace (not shown) and heated.

By this means, the solder layer is melted and the state of the solder 18a becomes as shown in FIG. 6. Here, the gold layer 17 of the electrode12 and the lower-end face of the thermoelectric element 13 aresubstantially in a state of contact, and the solder 18 a is accumulatedon the periphery of the bonded portion between the electrode 12 and thethermoelectric element 13. Further, the solder 18 a is prevented fromdropping by the visor portion 16 a. Upon removal from the reflow furnaceof the insulating substrate 11 and similar and cooling, the solder 18 ashrinks and hardens, assuming the state of FIG. 3. By this means, eachof the thermoelectric elements 13 is fixed to the insulating substrate11 via electrodes 12, resulting in the state of FIG. 7.

When fixing another insulating substrate 11 on the other end portion ofthe thermoelectric elements 13, electrodes 12 are formed in prescribedportions on the upper surface (after assembly, the lower surface) of theinsulating substrate 11, and two solder layers are formed, maintainingan interval between them respectively, on the upper faces of theelectrodes 12. The end portions of the thermoelectric elements are thenplaced on the upper faces of each of the solder layers, and theinsulating substrate 11, positioned above the thermoelectric elements13, is subjected to pressure by a weight or similar, placed into areflow furnace and heated, followed by external cooling. By fixing inplace the lead wires 14 a, 14 b to a prescribed electrode 12, thethermoelectric module 10 shown in FIG. 1 and FIG. 2 is obtained.

Thus in the thermoelectric module 10 of this aspect, anoutward-protruding visor portion 16 a is formed in the peripheralportion of the nickel layer 16 contained in the upper-end portions ofelectrodes 12. Hence when using solder 18 to fix the lower-end portionsof thermoelectric elements 13 to the upper faces of electrodes 12 formedon the upper surface of an insulating substrate 11, molten-state solder18 a overflowing from the bonded portion accumulates on the upper faceand side face of the visor portion 16 a, and dropping of the solder isprevented. By this means, it is possible to prevent the occurrence ofshort-circuits between electrodes 12 due to hardening of solder 18 awhich has flowed from different electrodes 12 onto the insulatingsubstrate 11 and made mutual contact.

Moreover, because electrodes are formed from three metal layers whichare a copper layer 15, nickel layer 16 and gold layer 17, with a visorportion 16 a formed in the nickel layer 16 having less solderabilitywith respect to solder 18, the molten-state solder 18 a can be morereliably prevented from passing the visor portion 16 a and flowing fromthe side face portion of the copper layer 15 to the side of theinsulating substrate 11. And, according to a method of manufacture of athermoelectric module 10 of this embodiment, the visor portion 16 a canbe formed by a simple method. Hence a thermoelectric module 10 can beobtained in which solder 18 a is prevented from flowing onto theinsulating substrate 11, and short-circuits between electrodes due tosolder 18 do not occur.

FIG. 8 shows a state in which an electrode 22 of a thermoelectric moduleof another embodiment of the invention is provided on the upper surfaceof an insulating substrate 21. This electrode 22 consists of a singlelayer, which is a nickel layer; a visor portion 26 a, protrudingoutward, is formed in the peripheral portion of the upper end. Theconfiguration of other portions of the thermoelectric module having suchelectrodes 22 is otherwise the same as in the above-describedthermoelectric module 10.

FIG. 9 is used to explain a method of formation of the electrode 22configured as described above. Here, as indicated in FIG. 9A, processesup to the formation of a pattern in the resist 29 on the upper surfaceof the insulating substrate 21 are the same as in the above-describedembodiment, therefore an explanation is omitted. After formation of thisresist, the above-described method is used to form electrodes consistingof a nickel layer within the resist 29. In this case, as indicated inFIG. 5B, the upper-end edge of the electrode 22 is also formed on aportion of the upper face of the resist 29.

Then, using a sodium hydroxide solution, the resist 29 is removed, andion beam etching is used to remove the seed layer formed below theresist 29, to obtain the state shown in FIG. 9C. By this means,electrodes 22 consisting of a nickel layer having a visor portion 26 aare formed in prescribed portions of the upper surface of the insulatingsubstrate 21. In this case also, a seed layer consisting of a chromiumlayer and a nickel layer is formed between the insulating substrate 21and the nickel layer of the electrodes 22. The method of fixing theelectrodes 22 and thermoelectric elements 13 in place by soldering isthe same as in the above-described embodiment, and so an explanation isomitted.

Thus in a thermoelectric module of this embodiment the number ofprocesses to form electrodes 22 is greatly reduced, so thatthermoelectric modules can be easily manufactured, and in addition costscan be reduced. According to this method of manufacture ofthermoelectric modules, the flowing of solder onto the insulatingsubstrate 21 can be prevented by a still simpler method, and athermoelectric module can be obtained in which short-circuits betweenelectrodes 22 due to solder do not occur.

Regarding another embodiment of the present invention, FIG. 10 shows astate in which an electrode 32 of the thermoelectric module is providedon the upper surface of an insulating substrate 31. This electrode 32consists of two metal layers, which are a magnesium layer 36 formed onthe upper face of a copper layer 35; a visor portion 36 a, protrudingoutward, is formed on the outer side of the periphery of the magnesiumlayer 36. The configuration of other portions of the thermoelectricmodule having these electrodes 32 is otherwise the same as theabove-described thermoelectric module 10.

Formation of this electrode 32 omits formation of the gold layer 17 inthe formation method illustrated in FIG. 5, and in place of formation ofthe nickel layer 16, a magnesium layer 36 is formed; otherwise themethod is the same as the formation method shown in FIG. 5, and anexplanation is omitted. When forming this electrode 32 also, the-numberof processes to form the electrode 32 is reduced, so that thethermoelectric module can easily be manufactured, and costs can bereduced. Further, by means of this thermoelectric module manufacturingmethod, a simple method can be used to prevent the flowing of solderonto an insulating substrate 31 and to obtain a thermoelectric module inwhich short-circuits between electrodes 32 due to solder do not occur.

Thermoelectric modules and manufacturing methods of this invention arenot limited to the above-described embodiments, and various appropriatealterations are possible. For example, the electrode 12 of anabove-described embodiment consists of three metal layers, with a visorportion 16 a provided in the nickel layer 16 which is formed as thesecond layer; however, this visor portion can be formed in the uppermostmetal layer. In this case, the thickness of the uppermost metal layer isset to 1 μm or greater.

In the electrode 32, a visor portion 36 a is provided in theupper-portion magnesium layer 36; but the visor portion may instead beprovided in the upper-end edge portion of the copper layer 35,positioned below the magnesium layer 36. Further, the magnesium layer 36and the visor portion 36 a in the electrode 32 may be formed integrallyas the same layer with substantially the same thickness; or, the lateralcross-section of the lower-side portion of the magnesium layer 36 may bemade the same as the lateral cross-section of the copper layer 35, withthe visor portion 36 a formed at the edge of the upper end of themagnesium layer 36.

Further, electrodes may be formed from three or more layers, and in thiscase the metal materials used in the different layers may be selectedand used as appropriate. For example, two layers may be formed on top ofa copper layer, one layer consisting of nickel and magnesium, the otherlayer of gold, tin, a tin alloy, or similar, with the visor portionformed at the edge of this second layer. In this case, the copper layerportion may be formed as two layers, with the other layer formed from ametal other than copper. In addition, the layer in which the upper visorportion is formed may be a single layer, and the layer in the lowerportion may consist of two or more layers.

In the method of formation of electrodes 22 shown in FIG. 9, electrodescan also be formed from a plurality of layers. And, the material used asthe solder 18 is not limited to tin and antimony, but can consist of tinand gold, tin and lead, and similar. The configurations of the otherportions in each of the above-described embodiments can also be modifiedas appropriate, within the technical scope of this invention.

1. A thermoelectric module, comprising: a pair of insulating substratesarranged in opposition; electrodes formed at prescribed locations onopposing inside surfaces of said insulating substrates; a plurality ofthermoelectric elements whose edge faces are soldered to respectiveopposing electrodes included in said electrodes, to fix in place saidthermoelectric elements between said pair of insulating substrates: anda visor portion protruding outward and formed on the edge portion ofsaid thermoelectric element on a side of said electrodes, whereby asolder is prevented from flowing from edge of said electrodes to saidinsulating substrates when said thermoelectric elements positioned onupper sides of said electrodes are soldered to said electrodes.
 2. Thethermoelectric module according to claim 1, wherein: said electrodescomprises a plurality of layers of different types of metals; and saidvisor portion is formed in a metal layer with less solderability withrespect to solder among said plurality of metal layers.
 3. Thethermoelectric module according to claim 1, wherein: said electrodescomprise three layers, which are a copper layer formed on one surface ofsaid insulating substrates, a nickel layer formed on one surface of saidcopper layer, and a gold layer formed on one surface of said nickellayer; and said visor portion is formed in said nickel layer.
 4. Thethermoelectric module according to claim 1, wherein said electrodescomprise a single layer of one type of metal.
 5. The thermoelectricmodule according to claim 1, wherein thickness of a root end and aprotruding length of said visor portion are respectively set to 1 μm orgreater.
 6. A manufacturing method for a thermoelectric module in which:a pair of insulating substrates are arranged in opposition; electrodesare formed at prescribed locations on the opposing inside surfaces ofsaid insulating substrates; and the end faces of a plurality ofthermoelectric elements are soldered to the respective opposingelectrodes, to fix in place said thermoelectric elements between saidpair of insulating substrates, said manufacturing method comprising: aresist layer formation step of forming a resist layer on one surface ofsaid insulating substrate; an exposure step of exposing the surface ofsaid resist layer, in a state of masking prescribed portions of thesurface of said resist layer formed in said resist layer formation step;a development step of removing the masked portions in said resist layerthrough development of the resist layer exposed in said exposure step toform a resist pattern; an electrode formation step of formingelectrodes, consisting of a plurality of metal layers, or said onesurface of said insulating substrate other than portions where saidresist pattern is formed in said development step; a resist layerremoval step of removing said resist layer of prescribed shape; and, anvisor formation step of removing a portion of the side portion of ametal layer on said insulating substrate side, among the plurality ofmetal layers of said electrodes, to form a visor portion on the edgeportion of said electrodes.
 7. The manufacturing method for athermoelectric module according to claim 6, wherein said visor portionis formed in a metal layer with less solderability with respect tosolder, among the plurality of metal layers of electrodes formed in saidelectrode formation process.
 8. The manufacturing method for athermoelectric module according to claim 6, wherein electrodes formed insaid electrode formation step comprise three layers, which are a copperlayer formed on one surface of said insulating substrates, a nickellayer formed on one surface of said copper layer, and a gold layerformed on one surface of said nickel layer, and said visor portion isformed in said nickel layer.
 9. A manufacturing method for athermoelectric module in which: a pair of insulating substrates arearranged in opposition; electrodes are formed at prescribed locations onthe opposing inside surfaces of said insulating substrates; end faces ofa plurality of thermoelectric elements are soldered to the respectiveopposing electrodes to fix said thermoelectric elements between saidpair of insulating substrates, said manufacturing method comprising: aresist layer formation step of forming a resist layer on upper surfaceof said insulating substrate; an exposure step of exposing surface ofsaid resist layer, in a state of masking prescribed portions of thesurface of said resist layer formed in said resist layer formation step;a development step of removing the masked portions in said resist layerthrough development of the resist layer exposed in said exposure step toform a resist pattern; an electrode formation step of forming electrodeson said upper surface of said insulating substrate other than portionswhere said resist pattern is formed in said development step and on aportion of the upper face of said resist layer to form a visor portionon the upper end edge portion of said electrodes; and, a resist layerremoval step of removing said resist layer of prescribed shape.